Surface fluorometry and transmission spectrophotometry of the oxidation-reduction state of NADH, flavoproteins, cytochromes, and myoglobin in isolated heart and lung mitochondria, cultured cardiac cells, and perfused heart and lung afford non-destructive, non-invasive approaches to a quantitation of localized and two-dimensional evaluation of hypoxia and response to injury to toxic substances. These approaches will be used in a variety of collaborative activities of the Center. The pulmonocardiac efficiency (PCE) in the delivery of oxygen to cardiac tissue is evaluated by surface fluorometry/reflectometry through light guides in contact with the epicardium of large and small animal models whose inspired oxygen is adjusted to a cardiac tissue pO2 sufficient to maintain the mitochondrial NADH of the heart 50% oxidized (0.05 torr). The model is then responsive to the efficiency of oxygen diffusion through the lung to the blood, the transport of oxygen from lung to heart, and the diffusion of oxygen from capillary to mitochondrion in normal, injured, and toxic conditions of the pulmonocardiac system. These in vivo approaches will be used in evaluating the other components of the Center activity. Development of fluorometric and spectrophotometric techniques and construction of biophysical equipment for use in experimental procedures and in demonstrations are requested as essential elements in the research proposed in this section, and form the focus of Core Facility section.